This invention relates to an extended buffer memory shared among a plurality of data processors and method of testing the extended buffer memory in accordance with a predetermined test program.
An extended buffer memory shared among a plurality of data processors is generally called a shared extended buffer memory and is operable to carry out a data transfer operation to and from one of the processors which is logically connected to the shared extended buffer memory. Each of the data processors comprises a central processing unit, a main memory unit, and a memory control unit. When one of the data processors requires the use of the shared extended buffer memory, the one of the data processors supplies a connection request to the shared extended buffer memory. If the shared extended buffer memory is vacant, the connection request is accepted. This means that the one of the data processors is logically connected to the shared extended buffer memory. When the one of the data processors is logically connected to the shared extended buffer memory, the other data processors have limited access to the shared extended buffer memory.
In the meanwhile, a test of the shared extended buffer memory should be periodically carried out to detect whether or not the shared extended buffer memory has a trouble or an obstacle. Any data processor can test the shared extended buffer memory in accordance with a predetermined test program. The test program is memorized in the main memory unit of each of the data processors. In practice, an operator gives a test execution instruction to one of the data processors through an instruction input device, such as a keyboard, to carry out the test of the shared extended buffer memory. In this event, the operator has to check whether or not the shared extended buffer memory is occupied. In other words, the operator has to check whether or not one of the data processors is logically connected to the shared extended buffer memory. If the one of the data processors occupies the shared extended buffer memory, the operator must wait for an input operation of the test execution instruction. At any rate, in a conventional shared extended buffer memory testing method, it is impossible to carry out the test of the shared extended buffer memory without a judgement of the operator.